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NATIONAL CONFERENCE : ROLE AND CHALLENGES

CHEMISTRY OF COFFEE ROASTING & AROMA

FORMATION

Presented by :

Anil Kumar Saini1, Aman Paul1, Sajan Palanchoke1, Sachin

Kumar Verma2

anil.cdfst@gmail.com

1M.Tech. Food Tech., Department of Food Process

Engineering, VSAET, SHIATS, Allahabad

2M.Sc. Dairy Technology, Department of Dairy Technology,

WSFDT, SHIATS, Allahabad

Presented by :

Anil Kumar Saini1, Aman Paul1, Sajan Palanchoke1, Sachin

Kumar Verma2

anil.cdfst@gmail.com

1M.Tech. Food Tech., Department of Food Process

Engineering, VSAET, SHIATS, Allahabad

2M.Sc. Dairy Technology, Department of Dairy Technology,

WSFDT, SHIATS, Allahabad

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INTRODUCTION

Coffee is brewed beverage with a dark, acidic flavor

prepared from the roasted seeds of the coffee plant, colloquially called

coffee beans. The beans are found in coffee cherries. Green coffee is one of

the most traded agricultural commodities in the world.

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Mesocarp

Spermorderm

Endocarp

Mucilaginous

PRO

CESS

ING

OF

GRE

EN

COF

FEE

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ChangesDuring

Roasting

Increased

in vol.(50-80%)

Green toBrowncolor

Weight

loss(13-20%)

Typicalroasterflavor ofbeans

Sp. Gravity

1.126-1.272 to

0.570-0.694

Horny,tough anddifficult to

crack beansbecome

brittle andmellow

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Composition of green and roasted coffees (according to variety) and of instant

coffee (expressed as a percentage of the dry basis)

Component Arabica

Green Roasted

Robusta

Green Roasted

Instant

Minerals 3.0-4.2 3.5-4.5 4.0-4.5 4.6 5.0 9-10

Caffeine 0.9-1.2 appox 1.0 1.6-2.4 appx2.0 4.5-5.1

Trigonelline 1.0-1.2 0.5-1.0 0.6-0 .75 0.3-0.6 -

Lipids 12-18 14.5-20 9.0-13.0 11.0-16.0 1.5-1.6

Total Chlorogenic

acids

5.5-8.0 1.2-2.3 7.0-10.0 3.9-4.6 5.2- 7.4

Aliphatic acids 1.5-2.0 1.0-1.5 1.5-2.0 1.0-1.5 -

Oligosaccharides 6.0-8.0 0-3.5 5.0-7.0 0- 3.5 0.7-5.2

Total Polysaccharides 50-55 24-39 37-47 - appx 6.5

Amino acids 2.0 0 2.0 0 0

Proteins 11.0-1.03 13.0-15.0 11.0-13.0 13.0-15.0 16.0-21.0

Humic acids - 16.0-17.0 - 16.0-17.0 15.0

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Protein denatured(500C).

Water evaporates.

Browning(1000C) due topyrolysis of organiccompound accompanied byswelling & an initial drydistillation.

Drying

ROASTING PHASES:

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Development

Release of volatile products at 1500C(H2O, CO CO2), results in increasein bean vol.

Some of the CO2 is absorbed within the texture of the roasted beans.

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Decomposition

At 150-2000C the beans being forced to popand burst along the groove.

Formation of bluish smoke and the release ofcoffee aroma.

Flavor produces

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Fullroasting

The moisture contents of beans drops to the level of 1.5-3.5%.

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Protein

Acid hydrolysatesby

30%

CHANGES IN PROTEINS:

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Sucrose &monosaccharid

e

Degraded&

Decompo

sed

Caramlizationof Sugars

CHANGES IN

CARBOHYDRATES:

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Diterpenes, Cafestol,

& Kahwoel

Degradedby roasting

Diterpene glycosides

CHANGES IN LIPIDS:

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Trigonelline(0.6%)decompos

ed upto50 %

Nicotinicacid

PyridineMethylEsters

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Volatile

acids,

Acetic

Acid

Formic

Acid

CHANGES IN ACIDS:

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Non-volatileacids

CitricAcid

Pyruvic

Acid

TartaricAcid

Lactic

Acid

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Chloroge

nic Acid

Decomposed70% by

strongerroasting

Decompos

ed 30% byroasting

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Malic acid

MesaconicAcidFumericAcid

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CitricAcid

ItaconicAcid

Mesacon

ic AcidCitaconic Acid

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CaffeineChlorpgenic

acid

Caffeine in addition to stimulation also contributes to the bitterness of the coffee.

(1:1)

CHANGES IN

CAFFEINE:

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Melanoids

MaillardReaction(carbohydratecaramelization)

Bitter flavor

Thermolysis of mixture ofcarbohydrate and protein.

MAILLARD REACTION:

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Pyrolysisofsucrose& othersugars

Pyrroles

Thiazoles &

Oxazoles

Thiophenes

Pyrazines

CHANGES IN OTHER CONSTITUES:

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Thermaldecomposition

of chlorogenicacids

Phenols

Carbonyl

esters

Polycycliccompoun

ds

Phenols

esters

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Carbohydratefragmentation

Alcohols

Carbonylcompounds

Alicycliccompounds

Hydrocarbons

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Light roastedUnroasted beanMedium & dark

roasted

Antioxidantactivity & totalPhenoliccontent

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Roasting condition

28 are odour volatilearomatic compoundscontribute strongly to thecoffee flavour .

Phenolic acidconcentration inroasted coffee

fresh note of coffeearoma, ( rapidly lost, &are considerable

indicators of freshness).

Methane, thioland 2, 3-

pentanedione

AROMA FORMATION:

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The results indicated that roasting degree significantly influenced the

colour, volatile compound, phenolic composition & antioxidant activity

of the coffee beans.

It is interesting to note that some phenolic acids increased while some

decreased in Catimor coffee beans after roasting, suggesting that heattreatment influenced both positively and negatively.

Therefore, it is extremely important to prepare coffee in a way that the

coffee has low enough level of phenolic acid to prevent acid reflux yet a

sufficient amount for antioxidant activities.

CONCLUSION

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